With the recent progress of communication networks such as mobile communication networks, facilities have to be provided for in order to intercept calls and/or connections in these networks. By intercepting these calls, law enforcement agencies such as the police or secret services are thus enabled to gather more information about suspicious or even criminal persons and to initiate suitable countermeasures against and/or to prosecute unlawful actions or the like.
It is to be noted that the present invention as described later on is not restricted to any type of communication network. For example, it is applicable to GSM communication networks as well as to more developed communication networks, like 3rd generation networks e.g. UMTS and so called All IP networks utilizing IM multimedia subsystem specified by 3GGP. Those more developed networks are for example described in the 3GPP specifications such as 3GPP TS 23.002 V5.4.0 (2001-10) and 3GPP TS23.228 V5.2.0 (2001-10). Also, a terminal means any user equipment by means of which a user/subscriber to the network may access the network, whether wireless or wirebound.
The communication networks may be assumed to have the standardized configuration except for the particularities explained in connection with the present invention. Therefore, a detailed description of the communication network architecture and/or involved functionality of the network entities is considered to be dispensable here as a skilled person may safely be aware of those aspects of communication networks.
Also, a detailed introduction to interception, i.e. lawful interception as such and the involved authorities and entities is considered to be known to skilled persons. For example, Kari Miettinen of the Department of Computer Science, University of Helsinki, Finland, has given a rather comprehensive overview over “Lawful Interception in GPRS/UMTS Network”, May 7, 1999. Although focusing on GPRS particularities in interception, the basic concepts as outlined in detail in chapter 2 still hold for the framework of the present invention. This means that the definitions of general principles (chapter 2.1.), standardized environment (chapter 2.2.), and parties and roles (chapter 2.3.) to a large extent can be applied to the present invention, so that a detailed description thereof can be omitted from the present specification.
In the currently existing implementation of legal interception the subscriber's call interception activation information is stored in the HLR's subscriber database and the HLR updates the call interception activation information in the MSC/VLR. The information is transferred either when the monitoring is activated or when the subscriber performs a location update. This way the interception information is present in the VLR serving the subscriber to be intercepted and can be activated when VLR detects any activities requiring legal interception. This method of activation is called VLR activation as it is the VLR that is playing the active role in activating interception.
The VLR activation described above is the default assumption in GSM networks, and thus the activation of the interception in the cases where the call to the subscriber is to be intercepted, is normally left for the VLR of the called subscriber (B-subscriber). This kind of assumption works fine if the B-subscriber is currently in his home network i.e. in the same network than this HLR is. Then the assumption that the VLR has the activation information is correct.
In the case where the B-subscriber to be intercepted is roaming in another network, this assumption that the VLR currently serving the B-subscriber knows the activation is no longer correct. Due to, for example, legal reasons information about the interception is not transferred from one network to another. Thus, the VLR currently serving the B-subscriber roaming in a different network can not activate the interception.
Due the above mentioned reason, in the currently existing implementation of GMSCs representing an access entity to a network constituting part of an interface to/from the network to e.g. another network, roaming subscribers cannot be intercepted according to VLR activation. Previously, the problem was solved so that the activations were set to a local database in a VLR of GMSC. When a new call was established via the GMSC the subscriber was searched from the local database in GMSC and interception was started according to the database. This type of solution required each GMSC to be informed about each subscriber marked to be intercepted and currently roaming in another network. As it is typical that each MSC also functions as a GMSC, this means that the information should be distributed to all MSC/VLR's in the network.
Stated in other words, in GSM networks the identity of a subscriber roaming in another network whose calls are to be legally intercepted has to be included in all VLR's. This results in a need to distribute a large amount of “intercepted target”—data in the network as each VLR has to be informed of the subscriber (i.e. his identity such as MSISDN or IMEI) to be intercepted, even if he is not present in the area of the VLR. Network operators have identified this as representing quite a drawback.